This invention relates to the method and apparatus for applying a uniformly thick adhesive layer to a planar substrate, and more particularly to a method and apparatus for applying a uniformly thick adhesive layer to a surface of an ink jet printhead part, wherein the adhesive layer thickness variation is controlled to a desired tolerance for each of a plurality of identical parts. After subsequent bonding to at least one other printhead part, the adhesive does not flow to undesired regions and obstruct the flow of ink in the assembled printhead, and the fillets of cured adhesive do not vary from printhead to printhead.
U.S. Pat, No. 4,678,529 to Drake et al. discloses a method of bonding ink jet printhead components together by spin coating or spraying a relatively thin, uniform layer of adhesive on a flexible substrate and then manually placing the flexible substrate surface with the adhesive layer against a printhead component surface. A uniform pressure and temperature is applied to ensure adhesive contact with all coplanar surface portions and then the flexible substrate peeled away, leaving a uniformly thin coating on the surfaces to be bonded. A roller or vacuum lamination may be applied to the flexible substrate to insure contact on all of the lands or coplanar surfaces of the printhead part. Unfortunately, this labor intensive method permitted adhesive layer thickness variation between a plurality of identical parts, so that ink flow characteristics varied from printhead to printhead.
U.S. Pat. No. 4,770,909 to McIntyre discloses the use of fluid porous roll applicators for applying coating materials. The coating was performed from room temperature to hot melt coating, including adhesives. The roll applicator is rotatable, hollow, and cylindrical with a microporous surface.